Carburetor



1964 H. A. CARLSON 3,

CARBURETOR 2 Sheets-Sheet l INVENTOR. HAROLD A. CARLSON Dec. 8, 1964 H. A. CARLSON 3,160,150

CARBURETOR Filed Aug. 29, 1963 2 Sheets-Sheet 2 FIG.8.

INVENTOR. HAROLD A. CARLSON AQENT United States Patent 3,160,150 canuunaron Harold A. Carlson, Brentwooel, Mo assignor to ACE ln- This invention relates to carburetors for internal combustion engines, and particularly to novel structures incorporating an automatic choke system for a carburetor. More specifically, the invention contemplates the provision of a carburetor for an internal combustion having means for automatically transitioning movement of the choke valve from a substantially closed position to a fully open position in response to engine temperatures and for eliminating undesired oscillation of the choke valve during the transition.

In starting an internal combustion engine under cold conditions, it is necessary that the choke valve be initially closed and upon firing of the engine that the choke valve move to a partially open position to allow entry of suflicient air to maintain combustion. As the engine temperature approaches the optimum operating range, the choke valve must move to andremain at a full open position to insure optimum engine performance.

Heretofore, a means for establishing the part and full open choke valve positions has been by the employment of a coiled thermostat spring which, when cold, urges the choke to a partially closed position and when warm, moves away from the choke operating lever allowing the choke valve to be forced to its fully open position by the force of air rushing into the carburetor. The choke valve may be mounted on the choke shaft in an olfcenter relation giving the choke valve a natural tendency to move to the open position. When the engine is started, a high manifold vacuum, which may be in the order of 18 inches of mercury, develops below the throttle and at fast idle speeds a subatmospheric pressure of a slightly lesser value is developed immediately below the choke valve thus causing atmospheric pressure to force the choke valve partially open. During relatively cold ambient temperature the force produced by the thermostat spring, tending to hold the choke valve closed, is considerable and even at the high manifold vacuum indicated above, the choke valve will be forced only slightly open by atmospheric pressure. The high vacuum indicated above induces a great quantity of fuel to flow from the fuel bowl to the mixture conduit while the flow of air into the mix-. ture conduit is restricted by the slightly opened choke causing the resultant mixture to be very rich. An overly rich mixture will cause rough idling as well as stalling of the engine and may result in flooding if the engine stalls. Since a larger flow of air is required to provide an optimum idle mixture it is obvious that either the choke must be further opened or a supplementary air flow must be provided. Opening the choke further, as described above is generally known in the art as vacuum break. A popular means of moving the choke valve to its partially open position upon starting of a cold engine has been the provision of a piston, which is operated by manifold vacuum and which is connected to the choke shaft in such a manner that manifold vacuum moving the piston will cause rotation of the choke shaft and movement of the choke valve to its partially open position.

Operation of the choke valve by means of a vacuum actuated piston has a number of disadvantages. The piston often sticks 'within its cylinder locking the choke valve in a position which renders the engine inoperative or inefficient in its operation requiring costly maintenance.

buretor wherein the choke valve thereof is modulated or ice a choke piston type carburetor also add to the expense of manufacture.

It is, therefore, an object of this invention to provide a carburetor for an internal combustion engine having a system for actuating the choke automatically in response to temperature conditions of the engine.

A further object of this invention is to provide a carburetor embodying an automatic choke system wherein undue oscillation or fluttering of the choke valve is substantially eliminated to achieve smooth engine operation While the engine is heating.

Another object of this invention is to provide a carburetor which is inexpensive to manufacture and reliable in use. An object of this invention is the provision'of a carpositively controlled throughout its movement.

It is among the objects of this invention to provide a carburetor including an automatic choke system which is easily and inexpensively repaired when servicing is necessary.

The invention embodies other novel features, details of construction and arrangement of parts which are hereinafter set forth in the specification and claims and illustrated in the accompanying drawings, forming part thereof, wherein:

FIGURE 1 is a schematic view illustrating a curburetor of this invention mounted on the engine of an automotive vehicle.

FIGURE 2 is an elevational view of this invention with parts broken away showing the fuel supply system in section.

FIGURE 3 is an elevational view of this invention.

PEGURES 4, 5, and 6 are partial elevational views showing various positions of the linkages.

FIGURE 7 is a partial sectional view showing the idle adjustment structure in detail.

FIGURE 8 is an enlarged side elevation view of arm 128.

Referring now to the drawing for a better understanding of the invention, there is indicated schematically at A in FIGURE 1 an automobile vehicle having an internal combustion engine E on which is mounted on carburetor C. Fuel for operation of the engine E is transported to the carburetor C from the fuel tank T of the vehicle under pressure supplied by fuel pump P as illustrated schematically in FIGURE 2. An exhaust manifold 2 is mounted on engine E to receive exhaust gases therefrom. An intake manifold 4 is mounted on engine E and adapted to supply the combustion chambers of the engine with combustible mixture. A thermostatically controlled heat riser 6 is connected to the exhaust manifold 2 and surrounds a portion of intake manifold 4 to heat the same and to heat the lower portion of carburetor C. A heat conduit 8 is connected between the exhaust manifold 2 and a thermostat'housing ill of carburetor C and transports hot exhaust gasses from the exhaust manifold to the thermostat housing to heat a thermostatic coil 12 in a manner to be discussed hereinbelow.

As illustrated in FIGURE 2, the carburetor C comprises a body casting Ztl formed with a vertical mixture conduit 25 and a fuel bowl 237. A throttle body portion 29 having a throttle bore 35 coaxial with and in continuation of mixture conduit .25 is located below the body casting 2t) and may either be integral with the body The cylinder, choke piston, and-the linkages necessary in or a separate casting, as illustrated The throttle body 29 is mounted on the intake manifold 4 by bolts 31 extending through openings in flange 33.

An air horn casting 37 is mounted on the body casting 26 by screws 39 and includes a bowl cover portion 41 closing the fuel bowl 27.

A fuel conduit 43 transports fuel from the fuel tank to the carburetor under pressure supplied by a fuel pump as indicated hereinabove and to a fuel inlet chamber 4-5 )rmed in air horn casting 3'7. Conduit 43 is threadedly ttached to casting 37 as shown in the embodiment illusated in FIGURE 2, but various other means of attachient inay be employed. A. fioat structure 51 is pivotally iounted from a pin 55 journaled in a depending portion f the air horn casting 37. A lever arm d4 of the float :ver 53 abuts the lower end of a needle valve 49 having t1 upper tapered end extendinginto a needle valve seat 9 of the inlet 47 to the fuel bowl 27. With the fuel level 1 bowl 27 low, as a result of fuel consumption by the ngine, the float 51 is lower and the lever arm 54 allows to valve 49 to be pressed by fuel pressure and gravity to n open position thus allowing a flow of fuel through the 1el inlet orifice. Fuel flows into the bowl 27 and upon :aching a predetermined level thefioat lever 54 presses pwardly against the needle valve 49 to close the inlet to 1e fuel bowl.

A choke shaft 61 is journaled in aligned bearing aperires within the air horn casting for rotary movement and choke valve, 65, fixed to the choke shaft within the air llet portion 63 of the air mixture conduit 25, is movable tom a position substantially closing the air inlet to a posion where the air inlet 63 is fully open. The choke valve is mounted on the choke shaft 61 in an off-center or nbalanced relation so that air rushing through the mix ire conduit tends to force the choke valve toward its 1113 open position. A thermostat, which may either be f the bimetallic coiled spring type, as illustrated at 12 in IGURE 2, or of the cross-over type, is connected to the hoke shaft in such a manner that the choke valve 65 will e biased closed by the bimetallic spring, when the theriostat is cold, and will be allowed to open when the theriostat reaches an optimum predetermined temperature. is illustrated in FIGURE 2, the free end 11 of the coiled iermostat spring 12, when cold, will-apply a counterclockise -rnovernent to an arm 13 fixed to the choke shaft e1 restrain the choke in its substantially closed position. is the thermostatic coil 1-2beginsto heat, it winds up and 1e free end 11 thereof will rotate clockwise thus allowig the chokevalve to move toward its open position as iscussedhereinabove.

A throttle shaft 67 is journaled in appropriately aligned earing apertures formed in the throttle body portion 29 f the carburetor C and extends transversely across throttle ore 35. A throttle valve 69 is fixed to the throttle shaft 7 within the throttle bore 35 and is movable from a posion whereit substantially closes throttle bore 35, as illus- .ated in FIGURES 2 and 3, to a position where the irottle bore is fully open. I

A boost vnturi 71 is formed integrally with the wall :ruct'ure of the mixture conduit 25 and has an inner veniri surface aligned coaxially with the mixture conduit 25 nd the primary ventnri surface 72.

Idle speed and high speed fuel systems for normal ngine operation are formed'in the carburetor body 28. L metering jet 73 is located in the bottom wall of the fuel owl 27 to permit the flow of fuel from the fuel bowl 7to the high speed and idle speed fuel circuits of the arburetbr. A vertically adjustable metering-rod '75 is ttached to the carburetor body 20 and has a lower shaped nd 74 adapted for adjustment within the jet '73 to vary the dective size thereof and thus to control the flow of fuel tom the'fuel bowl 27. A high speed fuel passage 77 is armed in body member 20 and is in communication with he fuel bowl 27 via metering jet 73 and with the mixture onduit 25 via a fuel nozzle 79, which is fitted into passage 7 at the upper end thereof. The fuel nozzle '79 extends rom the high speed fuel passage '77 into the boost venturi .nd is adapted to bleed a mixture of air and fuel into the oost venturi under the influence of the subatrnospheric lressure induced by air flowing through the boost venturi '1 and the primary venturi 72'. Air flows into the fuel to the choke shaft 61.

nozzle 7% through a passage 81 which is in communication with the atmosphere via a calibrated orifice 82.

An idle fuel an dair system is formed in the body member 2t? and the throttle body 29 and is adapted to supply a fuel and air mixture to the engine for low speed operation. The idle system comprises an idle fuel well 83 opening at its lower end into the high speed fuel passage 77. A calibrated idle fuel tube 85, having an open lower end extending below the level of fuel in well 85, is connected at its upper end to an idle fuel passage 87. An air bleed orifice 89 communicates. idle passage 87 with the atmosphere so that air is drawn into the idle passage by the subatmospheric pressure within the passage causing turbulence which agitates and emulsifiesthe fuel forming a rich mixture of fuel and air. An idle fuel chamber 91 is formed in the throttle body 29 and is in communication with idle passage 87. An elongated idle port 93 formed in the wall of the throttle body 29 establishes communication between the idle fuel chamber fiil and the throttle bore 35. The elongated idle port 93 is located adjacent the periphery of the throttle valve ea in such a manner that the throttle valve, in its substantially closed or curb idle position, closes a portion of'idle port 93. While the engine is at idle, air is drawn around the throttle valve sucking fuel from chamber 91 to throttle bore 35 under influence of high manifold vacuum. Manifold vacuum at idle speed may be in the order of 18 inches of mercury, depending upon'the type of engine employed. The rich mixture from the idle system is further mixed withair from the mixture conduit forming a correct idle mixture. An idle adjustment bore 915 is formed in the throttle body 29 below and in communication with idle chamber 91. Idle adjustment bore 95-is in communication with the throttle bore 35 by a small adjustable idle port W located downstream of throttle valve'69 and the idle port 93. An idle adjustment screw 99 having a conical shaped portion integral therewith is threaded into the bore 95 and is longitudinally adjustable within the bore 95 to vary the effective size of the port 97 thus varying the amount of mixtureflowing therefrom. The speed of the engine at normal idle is controlled by adjustment of the conical portion of screw 99 relative to the idle port 97.

The operation of theseveral fuel systems described hereinabove are well known in the 'art and a more detailed description at this time is not necessary for complete understanding of this invention.

Referring now to FIGURES 3 and 7, a choke arm 161 is fixed or otherwise attached to choke shaft 1 exteriorly of air horn casting 37. A connecting rod member 103 is pivotally connected at its upper end to arm 191 at a'position spaced from the choke shaft 61 and at its lower end to a choke actuating lever 119 to impart rotary movement A stud 105 having an elongated cylindrical shank portion 167 (FIGURE 7) and an enlarged cylindrical head portion 199 is threadedly attached to a boss 111 on the body member 20. A fast idle cam 113, two spacer members 115, a torsion spring 117 and the choke actuating lever 119 arelocated on shank portion 167 of stud 1495' and are rotatable with respect to stud 1%. An arm 121 (FIGURE 7) on the fast idle cam 113 is bent outwardly in relation to body 29 and substantially parallel to the centerline of stud 135. An arm 123 of the choke actuating lever 119 is bent inwardly toward the body memher 2% and substantially parallel to and in overlying relation with the arm 121 of fast idle earn 113. The torsion spring 117 is located on the shank It of studldS between the fast idle cam 113 and'the chokeactuating lever11 9, and separated fr'orn'the choke actuating ever and fast idle cam by spacers 115. The ends 125 of the spring 117 normally, maintain arms X21 and 123 in superposed relation in absence offorces which are operative to bias the arms apart.

A manually'actuated throttle control lever 127 is fixed to the throttle shaft 67 exteriorly of the throttle body 29 and is adapted to control various'mixture requirements of the engine. An idle adjustment finger 129 of the lever 127 is provided with an offset portionllfil for retaining a threaded curb idle adjustment screw 133 and a fast idlc adjustment screw 135 in threaded openings therein. The curb or normal idle adjustment screw 133 is adapted to contact the outer circumference 169 of the stud Hi (FI URE 6) and is adjusted longitudinally to maintain a de sired idle speed when the engine is warm. The fast idle adjustment screw 135 is arranged parallel to screw 133 and is adapted to contact the fast idle cam 113 (FIGURES 4 and 5), when the engine is cold. A throttle return spring 132 (FIGURE 3) which has one end thereof connected to a bracket 134 mounted on the engine E and the other end thereof connected to the throttle control arm 127 as shown in FIGURE 3, is adapted to rotate the throttle control arm 127 to its idle position. A throttle linkage 136, manually acuated by the operator, is adapted to impart counterclockwise rotation to arm 127.

As was explained hereinabove, the choke will not be allowed to open a sufiicient amount during cold idling conditions because the thermostat spring is strong enough to prevent manifold vacuum from opening the choke valve to the intermediate position. Therefore, a means is needed to overcome the force of the thermostat to break the vacuum during the initial stages of engine operation.

In accordance with a feature of this invention, a vacuum a break finger 128 is formed integral with the throttle lever 127 and is adapted, upon rotation of the throttle lever 127 in a clockwise direcion, as illustrated in FIGURES 3-6, to contact a laterally oifset finger 139 on the choke actuating lever 119 and to rotate the finger 13% together with the choke to a partially open choke position as illustrated in FIGURE 4. It is, therefore, seen that a novel extremely simple, durable and inexpensive structure is provided in accordance with the instant invention to eliminate an expensive choke actuating structure such as a vacuum actuated piston for choke actuation which has been popular heretofore in many types of carburetors. The offset finger 13%) extends in substantially parallel relation with the arms 121 and 12.3 and outwardly from the choke actuating lever 11% so that it is in a position tobe engaged by the vacuum break finger 128 as described above. When the engine E is relatively cold, starting is accomplished by manually holding the throttle 69 slightly open as illustrated in FIGURE 3 and cranking the engine. Before the engine fires the choke 65 will be biased completely closed by the thermostatic spring 12. When the engine starts the choke will be opened partially by manifold vacuum against the bias of the thermostatic spring 12 but the mixture will be overly rich. The operator will then release manual control of the throttle and the throttle lever 12'? will be rotated clockwise by the throttle return spring causing the arm 12% to engage the finger 3.3% and move the choke 65 to the position shown in FIGURE 4. At this predetermined position the air and fuel ratio will be proper, achieving smooth idling. As the choke actuating lever 119 is moved by the arm 128 to the position illustrated in FIG- UR'E 4, the fast idle cam 113, since it is normally positioned relative to the choke actuating lever 119 by engagement of the arms 121 and 123 by the ends 125 torsion spring 17, will be rotated along with the choke actuating lever 11% and will present a series of steps in a position to be engaged by the fast idle adjustment screw 135. It will be understood that the engine will be operating in a fast idle, partially choked condition when the throttle-choke actuating structures are positioned as illustrated in FIG- URE 4.

If the operator decides to allow the engine to operate at fast idle until optimum operating temperature is reached,-

the arrangement of parts is such that the engine will not become over-choked as the temperature rises. As the choke 65 begins to move toward its open position by heating of the thermostat 12, the choke actuating lever will be forced to rotate against the bias of the torsion spring 117' by the connection link 1% while the fast idle cam is restra ned in its fast idle position, as shown in FIGURE 5, by the fast idle adjustment screw 135. In this condition the engine will be idling fast and the choke will be open allowing the engine to operate smoothly. It will be understood-that the engine is allowed to automatically transition itself from a fast idle choked condition to a fast idle open choke condition in response to heating requirements of the engine.

To return the engine to its normal idle open choke condition after proper heating has occurred, the operator merely manually rotates the throttle control arm counterclockwise (FIGURE 3) to a position where the fast idle adjustment screw 135 is clear of the fast idle cam 113. The torsion spring 117, since it is no longer held byforce of the fast idle adjustment screw 135, will then immediately rotate the fast idle cam 113 clockwise to align arms 121 and 123 in superposed relation as set forth hereinabove. The elements, when at curb idle, will then be in a position as shown in FIGURE 6 with the idle adjustment screw 133 in contact with the head of the stud and the choke 65 in its fully opened condition.

In accordance with another feature of this invention, a thin leaf spring 143 is attached to the contacting face 145 of the vacuum break finger I23 and interposed between the fingers 128 and 13b, for the purpose of modulating the choke and for preventing any tendency of the choke valve to flutter when the pressure between the fingers 128 and 130 approaches Zero. In its normal position, the free end of the leaf spring is spaced from the face 145 of the finger as illustrated in FIGURE 8. The leaf spring 143 is of much less compressive value than that of the choke coil spring 12 and of greater compressive value than that of the torsion spring 117. Therefore, when the choke coil is cold and biases the choke valve to its closed condition the same biasing force will be applied between fingers 123 and 13% causing the free end of spring 143 to be forced into abutting relationship with the face 145 of finger 128. As the choke coil bias relaxes due to heating thereof and a preaches zero, the leaf spring 143 bearing against the finger will move the lever 119 clockwise a small amount thus moving the choke toward its open position a small amount. As the thermostat continues to heat, the spring 143 will continue to gradually urge the lever 119 in a clockwise direction thus moving the choke valve toward its open position until the spring 143 is fully expanded. At this point, however, air rushing into the mixture conduit will provide enough force to positively urge the choke further toward its open position. It will be understood that the choke is modulated or positively controlled at all stages of movement toward its open position. This same positive choke control also prevents choke flutter during movement of the choke to the open position. When the thermostat bias, tending to close the choke, and bias tending to open the choke reach an equilibrium, the choke valve may oscillate or flutter a small amount causing uneven operation of the engine. The spring 143 prevents this occurrence my positively moving the choke valve to a position where air pressure positively takes over and continues to move the choke toward the open position. It will be understood that at no time is the choke valve allowed to be free to oscillate or flutter. The engine will operate smoothly at all phases of choke operation. I

Certain structures have been described herein which will fulfill all of the objects of the present invention, but

r throttle shaft journaled in said body structure and extending across said mixture conduit, a throttle valve fixed to said throttle shaft and positioned within said mixture conduit for movement from an open position to a position 7? closing said mixture conduit, a throttle lever fixed to said ;hrottle shaft for operating said throttle valve, a choke shaft journaled in said body structure and extending across said mixture conduit anteriorly of said throttle shaft, a choke valve fixed to said choke shaft within said mixture conduit for movement from an open position to a position closing said mixture conduit, means for operating said choke valve, thermally responsive means positioned on said body structure and adapted when the engine is cold to bias said choke valve to said closed position, said thermally responsive means, upon heating thereof, adapted to move to a position where it no longer applies said bias to said choke valve thus allowing said choke valve to be moved by air pressure toward said open position, means on said throttle lever for moving said choke valve to a predetermined intermediate position against the bias of said thermally responsive means, under coldengine conditions, after said engine has started.

2. A fuel and air mixture device for an internal combustion engine, said device comprising a body structure having an air and fuel mixture conduit therethrough, a throttle shaft journaled in said body structure and extending across said mixture conduit, a throttle valve fixed to said throttle shaft and positioned within said mixture conduit for movement from an open position to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft for operating said throttle valve, a choke shaft journaled in said body structure and extending across said mixture conduit anteriorly of said throttle shaft, a choke valve fixed to said choke shaft within said mixture conduit for movement from an open position to a position closing said mixture conduit, means for operating said choke valve, thermally responsive means positioned on said body structure and being in operative contact with said choke operating means when the engine is cold to bias said choke valve to said closed position, said thermally responsive means, upon heating thereof, adapted to move out of said operative contact, thus allowing said choke valve to be moved by air pressure toward said open position, means on said throttle lever for moving said choke valve to a predetermined intermediate position against thebias of said thermally responsive means, under cold engine conditions, after said engine has started.

3. A fuel and air mixture device for an internal combustion engine, said device comprising a body structure having an air and fuel mixture conduit therethrough, a throttle shaft journaled in said body structure and extending across said mixture conduit, a throttle valve fixed to said throttle shaft and positioned within said mixture conduit for movement from an open position to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft for operating said throttle valve, a choke shaft journaled in said body structure and extending across said mixture conduit anteriorly of said throttle shaft, a choke valve fixed to said cho (e shaft within said mixture conduit for movement from an open position to a position closing said mixture conduit, means for operating said choke valve, thermally responsive means positioned on said body structure and being in operative contact with said choke operating means when the engine is cold to bias said choke valve to said closed position, said thermally responsive means upon heating thereof adapted to move out of said operative contact, thus allowing said choke valve to be moved by air pressure toward said open position, finger means on said throttle lever adapted to engage said choke operating means for moving said choke valve to a predetermined intermediate position against the bias of said thermally responsive means, under cold engine conditions, after said engine has started.

4. A fuel and air mixture device for an internal combustion engine, said device comprising a body structure having an air and fuel mixture conduit therethrough, a"

throttle shaft journaled in said body structure and extending across said mixture conduit, a throttle valve fixed to said throttle shaft and positioned within said mixture conduit for movement from an open position to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft for operating said throttle valve, a choke shaft journaled in said body structure and extending across said mixture conduit anteriorly of said throttle shaft, a choke valve fixed to said choke shaft within said mixture conduit for movement from an open position to a position closing said mixture conduit, a choke shaft arm fixed to said choke shaft exteriorly of said body structure, a choke operating lever having a laterally offset finger thereon being pivotally attached to said body, a linkage between said choke shaft and said choke operating lever for transmitting rotary movement of said lever to said choke shaft for operating said choke valve, thermally responsive means positioned on said body structure and being in operative contact with said choke shaft arm when the engine is cold to bias said choke valve to said closed position, said thermally responsive means upon heating thereof adapted to move out of said operative contact, thus allowing said choke valve to be moved by air pressure toward said open position, a finger integral with said throttle lever adapted to engage said laterally offset finger for moving said choke valve to a predetermined intermediate position against the bias of said thermally responsive means, under cold engine conditions.

5. A carburetor for an internal combustion engine comprising a body formed with a mixture conduit adapted to be vertically disposed and having an inlet, an outlet and a venturi surface disposed between said inlet and outlet, a throttle shaft journaled in said body and extending across said mixture conduit, a throttle valve secured to said shaft within said mixture conduit and movable from a position opening to a position closing said mixture conduit, a choke shaft journaled in said body adjacent said inlet arid extending across said mixture conduit, a choke valve fixed to said choke shaft within said mixture conduit'and movable from. a position closing to a position opening said mixture conduit, thermally responsive means positioned on said body and adapted'to bias said choke valve to said closed position when said engine is'relatively cold, means for heating said thermally responsive means in response to operation of said engine, means for moving said choke valve, when said engine is cold, from said closed position to a predetermined partially open posi tion against the bias of Sfllld thermally responsive means, and means for modulating said choke valve and for pre venting undue oscillation thereof when the bias of said thermally responsive means on said choke valve and the forces produced by air on said choke valve become approximately equal.

6. A carburetor for an internal combustion engine comprising a body formed with a mixture conduit adapted to be vertically'disposed and having an inlet, an outlet and a venturi surface disposed between said inlet and outlet, a throttle shaft journaled in said body and extending across said mixture conduit, a throttle valve secured to said shaft within said mixture conduit and movable from a position opening to a position closing said mixture conduit, a choke shaft journaled in said body adjacent said inlet and extending across said mixture conduit, a choke valve'fixed to said choke shaft within said mixture conduit, and movable from a position closing to'a position opening said mixture conduit, thermally responsive means positioned on said body and adapted to bias said choke valve to said closing position when said engine is relatively cold, means for heating said thermally responsive means in response to operation of said engine, means for moving said choke Q valve and the forces produced by air on said choke valve become approximately equal.

7. A carburetor for an internal combustion engine comprising a body formed with a mixture conduit adapted to be vertically disposed and having an inlet, an outlet and a venturi surface disposed between said inlet and outlet, a throttle shaft journaled in said body and extending across said mixture conduit, a throttle valve secured to said shaft within said mixture conduit and movable from a position opening to a position closing said mixture conduit, means for operating said throttle, a choke shaft journaled in said body anteriorly of said throttle valve and extending across said mixture conduit, a choke valve fixed to said choke shaft within said mixture conduit, and movable from a position closing to a position opening said mixture conduit, means for operating said choke, thermally responsive means positioned on said body and adapted to bias said choke valve to said closed position when said engine is relatively cold, means for heating said thermally responsive means in response to operation of said engine, a finger on said throttle operating means for engagement with said choke operating means for moving said choke valve, when said engine is cold, from said closed position to a predetermined partially open position against the bias of said thermally responsive means after said engine has started, a fast idle cam positioned on said body, a fast idle adjustment means positioned on said throttle operating means and adapted to engage said fast idle cam for maintaining said engine at fast idle speed during opening of said choke valve and a spring positioned on said finger and extending between said finger and said choke operating means for modulating said choke valve during initial opening thereof and for preventing undue oscillation thereof when the bias of said thermally responsive means on said choke valve and the forces produced by air on said choke valve ecome approximately equal.

8. A carburetor for an internal combustion engine comprising a body formed with a mixture conduit adapted to be vertically disposed and having an inlet, an outlet and a venturi surface disposed between said inlet and outlet, a throttle shaft journaled in said body and extending across said mixture conduit, a throttle valve secured to said shaft within said mixture conduit and movable from a position opening to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft for operating said throttle valve, a choke shaft journaled in said body adjacent said inlet and extending across said mixture conduit, a choke valve fixed to said choke shaft Within said mixture conduit and movable from a position closing to a position opening said mixture conduit, thermally responsive means positioned on said body and adapted to bias said choke valve to said closing position when said engine is relativelycold, means for heating said thermally responsive means in response to operation of said engine, means for moving said choke valve, when said engine is cold, from said closing position to a predetermined partially open position against the bias of said thermally responsive means after said engine has started, a fast idle cam pivotally mounted on said body, a fast idle adjustment means positioned on said throttle operating means and adapted to engage said fast idle cam when said engine is cold for maintaining said engine at fast idle speed while said choke valve opens, a leaf spring positioned on said finger, said spring having a free end thereof in spaced relation with said finger and extending between said finger and said choke operating means for modulating said choke valve during initial movement of said choke valve and for preventing undue oscillation thereof when the bias of said thermally responsive means on said choke valve and the forces produced by air on said choke valve become approximately equal.

9. A carburetor for an internal combustion engine comprising a body formed with a mixture conduit adapted to be vertically disposed and having an inlet, an outlet and a venturi surface disposed between said inletand outlet, a

throttle shaft jou'rnaled in said body and extending across said mixture conduit, a throttle valve secured to said shaft within said mixture conduit and movable from a position opening to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft for operating said throttle valve, a choke shaft journaled in said body anteriorly of said throttle valve and extending across said mixture conduit, a choke valve fixed to said choke shaft within said mixture conduit, a movable from a position closing to a position open said mixture conduit, means for operating said choke valve, thermally responsive means positioned on'said body and adapted to bias said choke valve to said closed position when said engine is relatively cold, means for heating said thermally responsive means in response to operation of said engine, a finger on said throttle operating means for engagement With said choke operating means for moving said choke valve, when said engine is cold, from said closed position to a predetermined partially open position against the bias of said thermally responsive means after said engine has started, means for maintaining said engine at fast idle speed while said choke valve opens and a spring fixed to said finger and having a freerend thereof spaced from said finger and extending between said finger and said choke operating means, said spring being of less compressive value than said thermally responsive means whereby the free end of said spring will be compressed into engagement with said finger when said engine is cold, said free end of said spring adapted upon warming of said thermally responsive means to move away from said finger, to impart an initial rotation to said choke valve and to prevent oscillation of said choke valve when the bias of said thermally responsive means on said choke valve and the forces produced by air on said choke valve become approximately equal.

10. A fuel and air mixture device for an internal combustion engine, said device comprising a body structure having an air and fuel mixture conduit therethrough, a

ing said throttle valve, a choke shaft journaled in bearing apertures in said body structure and positioned across said mixture conduit, a choke valve fixed to said choke shaft Within said mixture conduit anteriorly of said throttle valve and being movable from an open position to a position closing said mixture conduit, means for operating said choke valve, said means including an arm fixed to said choke shaft, thermally responsive means fixed to said body structure and being in operative contact with said choke shaft arm when the engine is cold to bias said choke valve tovsaid closed position, said thermally responsive means, upon heating thereof, adapted to move out of said operative contact, means for engagement with said choke operating means and adapted to move said choke valve toward said open position when the bias of said thermally responsive means and the force of air pressure upon said choke valve become substantially equal, whereby said choke valve will be positively urged toward said open position and the possibility of choke valve oscillation during movement thereof will be eliminated.

11. A fuel and air mixture device for an internal combustion engine, said device comprising a body structure having an air and fuel mixture conduit therethrough, a throttle shaft journaled in said body structure and extending across said mixture conduit, a throttle valve fixed to said throttle shaft and movable from an Open position to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft and being rotatable for operating said throttle valve, a choke shaft journaled ir bearing apertures in said body structure and positionet' :hoke shaft within said mixture conduit anteriorly of said hrottle valve and being movable from an open position a position closing said mixture conduit, means for )perating said choke valve, said means including an arm ixed to said choke shaft exteriorly of said body structure, :herrnally responsive means fixed to said body structure and being in operative contact with said choke shaft arm when the engine is cold to bias said choke valve to said :losed position, said thermally responsive means, upon :ieating thereof, adapted to move out of said operative :ontact to a position Where it no longer applies'said bias :0 said choke shaft arm, resilient means for engagement with said choke operating means and adapted to move said choke valve toward said open position when the bias of said thermally responsive means and the forcetof air pressure upon said choke valve become substantially equal, whereby said choke valve is positively urged toward its open position by said resilient means and the possibility of choke valve oscillation during movement thereof is eliminated.

12. A fuel and air mixture device for an internal comaustion engine, said device comprising'a body structure having an air and fuel mixture conduit therethrough, a throttle shaft journaled in said body structure and ex tending across said mixture conduit, a throttle valve fixed :0 said throttle shaft and movable from an open position to a position closing said mixture conduit, a throttle lever [ixed to said throttle shaft and being rotatable for operating said throttle valve, a choke shaft journaled in bearing apertures in said body structure and positioned across said mixture conduit, a choke valve fixed to said choke shaft within said mixture conduit anteriorly of said throttle valve and being movable from an open position to a position closing said mixture conduit, means for operating said choke valve, said means including an arm fixed to said choke shaft exteriorly of said body structure, thermally responsive means fixed to said body structure and being in operative contact with said'choke shaft arm, when the engine is cold, to bias said choke valve to said :losed position, said thermally responsive means, upon heating thereof, adapted to move out of said operative :ontact to a position where it no longer applies said bias to said choke shaft arm, resilient means on said throttle operating means and adapted for engagement with said :hoke operating means to move, said choke valve toward said open position when the bias of said thermally responsive means and the force of air pressure upon said choke valve become substantially equal, whereby said choke valve will be positively urged toward said open position by said resilient means and the possibility of choke valve oscillation during movement thereof will be elimi hated. V

13. A fuel and air mixture device for an internal combustion engine, said device comprising a body structure having an air and fuel mixture conduit therethrough, a throttle shaft journaled in said body structure and extending across said mixture conduit, a throttle valve fixed to said throttle shaft and movablefrom an open position to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft and being rotatable for operating said throttle valve, a choke shaft journaled in bearing apertures in said body structure and positioned across said mixture conduit, a choke valve fixed tonsaidchoke art i2 shaft within said mixture conduit anteriorly of said throttle valve and being movable from an open position to a position closing said mixture conduit, means for operating said choke valve, said means including an arm fixed to said choke shaft exteriorly of said body structure, thermally responsive means fixed to said body structure and being in operative contact with said choke shaft arm,

When the engine is cold, to bias said choke valve to said closed position, said thermally responsive means, upon heating thereof, adapted to move out of said operative contact to a position where it no longer applies said bias to said choke shaft arm, a spring fixed to said throttle operating means for engagement with said chokeoperating means and adapted to move said choke valve toward said open position when the bias of said thermally responsive means and the force, of air pressure upon said choke valve become substantially equal, whereby said choke valve will be positively urged toward said open position by said resilient means and the possibility of choke valve oscillation during movement thereof will be eliminated.

14. A fuel and air mixture device for an internal combustion engine, said device comprising a body structure having an air and fuel mixture conduit there/through, a throttle shaft journaled in said body structure and extending across said mixture conduit, a throttle valve fixed to said throttle shaft and movable from an open position to a position closing said mixture conduit, a throttle lever fixed to said throttle shaft and being rotatable for operating said throttle valve, a choke shaft journaled in bearing apertures in said body structure and positioned across said mixture conduit, a choke valve fixed to said choke shaft within said mixture conduit anteriorly of said throttle valve and being movable from an open position to a position closing said mixture conduit, means for operating said choke valve, said means including an arm fixed to said choke shaft exteriorly of said body structure, thermally responsive means fixedto said body structure and being in operative contact with said choke shaft arm, when the engine is cold, to bias said choke valve to said closed position, said thermally responsive means, upon heating thereof, adapted to move out of said operative contact to a position where it no longer applies said bias to said choke shaftarm, a leaf spring fixed to said throttle operating means for engagement with said choke operating means and adapted to move said choke valve toward said open position when the bias of said thermally responsive means and the force of air pressure upon said choke valve become substantially equal, vWhereby said choke valve will be positively urged toward said open position by said resilient means and the possibility of choke valve oscillation during movement thereof will be eliminated.

References Cited by the Examiner UNITED STATES PATENTS 2,124,777 7/38 Hunt 26l52 2,307,486 l/43 Carlson 26152 2,867,424 1/59 Sutton 26152 3,006,618 10/61 Carlson et al. 261-- 52 RICHARD B. WILKINSON, Primary Examiner.

KARL I. ALBRECHT, Examiner. 

1. A FUEL AND AIR MIXTURE DEVICE FOR AN INTERNAL COMBUSTION ENGINE, SAID DEVICE COMPRISING A BODY STRUCTURE HAVING AN AIR AND FUEL MIXTURE CONDUIT THERETHROUGH, A THROTTLE SHAFT JOURNALED IN SAID BODY STRUCTURE AND EXTENDING ACROSS SAID MIXTURE CONDUIT, A THROTTLE VALVE FIXED TO SAID THROTTLE SHAFT AND POSITIONED WITHIN SAID MIXTURE CONDUIT FOR MOVEMENT FROM AN OPEN POSITION TO A POSITION CLOSING SAID MIXTURE CONDUIT, A THROTTLE LEVER FIXED TO SAID THROTTLE SHAFT FOR OPERATING SAID THROTTLE VALVE, A CHOKE SHAFT JOURNALED IN SAID BODY STRUCTURE AND EXTENDING ACROSS SAID MIXTURE CONDUIT ANTERIORLY OF SAID THROTTLE SHAFT, A CHOKE VALVE FIXED TO SAID CHOKE SHAFT WITHIN SAID MIXTURE CONDUIT FOR MOVEMENT FROM AN OPEN POSITION TO A POSITION CLOSING SAID MIXTURE CONDUIT, MEANS FOR OPERATING SAID CHOKE VALVE, THERMALLY RESPONSIVE MEANS POSITIONED ON SAID BODY STRUCTURE AND ADAPTED WHEN THE ENGINE IS COLD TO BIAS SAID CHOKE VALVE TO SAID CLOSED POSITION, SAID THERMALLY RESPONSIVE MEANS, UPON HEATING THEREOF, ADAPTED TO MOVE TO A POSITION WHERE IT NO LONGER APPLIES SAID BIAS TO SAID CHOKE VALVE THUS ALLOWING SAID CHOKE VALVE TO BE MOVED BY AIR PRESSURE TOWARD SAID OPEN POSITION, MEANS ON SAID THROTTLE LEVER FOR MOVING SAID CHOKE VALVE TO A PREDETERMINED INTERMEDIATE POSITION AGAINST THE BIAS OF SAID THERMALLY RESPONSIVE MEANS, UNDER COLD ENGINE CONDITIONS, AFTER SAID ENGINE HAS STARTED. 